Just a note about the box you have installed. I bought one from Lowes made for an RV hookup. Two things missing, first was a disconnect switch, the other was a 20 amp outlet.
I am an old electrician and forgot these two things. Most here suggest turning off the power before plugging in the RV. I agree. A CB somewhere else is not a disconnect switch and should not be used as one. When we had the house built, code called for ONE 15 amp duplex outlet in the garage and no exterior outlets. I upgraded to an outlet every six feet all on GFCI outlets and one 15 amp exterior outlet. I should have gone with multiple 20 GFCI's including a 20 amp exterior outlet.
I pulled #10 and #12 wires and have now upgraded. Would have been easier to do it all the first time.